package balance

import (
	"testing"

	"github.com/seaweedfs/seaweedfs/weed/admin/topology"
	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
	"github.com/seaweedfs/seaweedfs/weed/storage/super_block"
	"github.com/seaweedfs/seaweedfs/weed/worker/types"
)

func rp(t *testing.T, code string) *super_block.ReplicaPlacement {
	t.Helper()
	r, err := super_block.NewReplicaPlacementFromString(code)
	if err != nil {
		t.Fatalf("invalid replica placement code %q: %v", code, err)
	}
	return r
}

func loc(dc, rack, node string) types.ReplicaLocation {
	return types.ReplicaLocation{DataCenter: dc, Rack: rack, NodeID: node}
}

func TestIsGoodMove_NoReplication(t *testing.T) {
	// 000 = no replication. Any move is fine.
	if !IsGoodMove(rp(t, "000"), []types.ReplicaLocation{loc("dc1", "r1", "n1")}, "n1", loc("dc1", "r1", "n2")) {
		t.Error("000: any move should be allowed")
	}
}

func TestIsGoodMove_001_SameRack(t *testing.T) {
	// 001 = 1 replica on same rack (2 total on same rack)
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc1", "r1", "n2"),
	}
	// Move n1 -> n3 on same rack: good
	if !IsGoodMove(rp(t, "001"), existing, "n1", loc("dc1", "r1", "n3")) {
		t.Error("001: move to same rack should be allowed")
	}
	// Move n1 -> n3 on different rack: bad (would leave only 1 on r1, need 2)
	if IsGoodMove(rp(t, "001"), existing, "n1", loc("dc1", "r2", "n3")) {
		t.Error("001: move to different rack should not be allowed when it breaks same-rack count")
	}
}

func TestIsGoodMove_010_DiffRack(t *testing.T) {
	// 010 = 1 replica on different rack (2 racks total)
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc1", "r2", "n2"),
	}
	// Move n1 -> n3 on r2: bad (both replicas on same rack)
	if IsGoodMove(rp(t, "010"), existing, "n1", loc("dc1", "r2", "n3")) {
		t.Error("010: move to same rack as other replica should not be allowed")
	}
	// Move n1 -> n3 on r3: good (still 2 different racks)
	if !IsGoodMove(rp(t, "010"), existing, "n1", loc("dc1", "r3", "n3")) {
		t.Error("010: move to different rack should be allowed")
	}
}

func TestIsGoodMove_100_DiffDC(t *testing.T) {
	// 100 = 1 replica in different DC
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc2", "r1", "n2"),
	}
	// Move n1 -> n3 in dc2: bad (both in same DC)
	if IsGoodMove(rp(t, "100"), existing, "n1", loc("dc2", "r1", "n3")) {
		t.Error("100: move to same DC as other replica should not be allowed")
	}
	// Move n1 -> n3 in dc3: good (different DCs)
	if !IsGoodMove(rp(t, "100"), existing, "n1", loc("dc3", "r1", "n3")) {
		t.Error("100: move to different DC should be allowed")
	}
}

func TestIsGoodMove_SameNode(t *testing.T) {
	// Moving to the same node as an existing replica should always be rejected
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc1", "r2", "n2"),
	}
	if IsGoodMove(rp(t, "010"), existing, "n1", loc("dc1", "r2", "n2")) {
		t.Error("should reject move to same node as existing replica")
	}
}

func TestIsGoodMove_011_Composite(t *testing.T) {
	// 011 = 1 same-rack + 1 different-rack (3 replicas: 2 on same rack, 1 on different)
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc1", "r1", "n2"),
		loc("dc1", "r2", "n3"),
	}
	// Move n1 -> n4 on r1: good (maintains 2 on r1, 1 on r2)
	if !IsGoodMove(rp(t, "011"), existing, "n1", loc("dc1", "r1", "n4")) {
		t.Error("011: move within same rack should be allowed")
	}
	// Move n3 -> n4 on r1: bad (would have 3 on r1, 0 on different rack)
	if IsGoodMove(rp(t, "011"), existing, "n3", loc("dc1", "r1", "n4")) {
		t.Error("011: move that eliminates different-rack replica should not be allowed")
	}
}

func TestIsGoodMove_110_Composite(t *testing.T) {
	// 110 = 1 different-rack + 1 different-DC (3 replicas across 2 DCs and 2 racks)
	existing := []types.ReplicaLocation{
		loc("dc1", "r1", "n1"),
		loc("dc1", "r2", "n2"),
		loc("dc2", "r1", "n3"),
	}
	// Move n1 -> n4 in dc1/r3: good (dc1 still has r2+r3, dc2 has r1)
	if !IsGoodMove(rp(t, "110"), existing, "n1", loc("dc1", "r3", "n4")) {
		t.Error("110: move to new rack in same DC should be allowed")
	}
	// Move n3 -> n4 in dc1/r1: bad (would lose the different-DC replica)
	if IsGoodMove(rp(t, "110"), existing, "n3", loc("dc1", "r1", "n4")) {
		t.Error("110: move that eliminates different-DC replica should not be allowed")
	}
}

func TestIsGoodMove_NilReplicaPlacement(t *testing.T) {
	if !IsGoodMove(nil, []types.ReplicaLocation{loc("dc1", "r1", "n1")}, "n1", loc("dc1", "r1", "n2")) {
		t.Error("nil replica placement should allow any move")
	}
}

func TestCalculateBalanceScore_ReplicationAware(t *testing.T) {
	disk := func(dc, rack string) *topology.DiskInfo {
		return &topology.DiskInfo{
			DataCenter: dc,
			Rack:       rack,
			DiskInfo:   &master_pb.DiskInfo{MaxVolumeCount: 100, VolumeCount: 50},
		}
	}

	// 001: same-rack replication — should prefer same rack and same DC
	rp001 := rp(t, "001")
	sameRack := calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, rp001)
	diffRack := calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp001)
	diffDC := calculateBalanceScore(disk("dc2", "r2"), "r1", "dc1", 0, rp001)
	if sameRack <= diffRack {
		t.Errorf("001: same-rack score (%v) should exceed different-rack score (%v)", sameRack, diffRack)
	}
	if sameRack <= diffDC {
		t.Errorf("001: same-rack score (%v) should exceed different-DC score (%v)", sameRack, diffDC)
	}

	// 010: different-rack replication — should prefer different rack, same DC
	rp010 := rp(t, "010")
	sameRack = calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, rp010)
	diffRack = calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp010)
	if diffRack <= sameRack {
		t.Errorf("010: different-rack score (%v) should exceed same-rack score (%v)", diffRack, sameRack)
	}

	// 100: different-DC replication — should prefer different DC
	rp100 := rp(t, "100")
	sameDC := calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp100)
	diffDCScore := calculateBalanceScore(disk("dc2", "r2"), "r1", "dc1", 0, rp100)
	if diffDCScore <= sameDC {
		t.Errorf("100: different-DC score (%v) should exceed same-DC score (%v)", diffDCScore, sameDC)
	}

	// nil rp: should prefer cross-rack/DC (default behavior)
	sameRack = calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, nil)
	diffRack = calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, nil)
	if diffRack <= sameRack {
		t.Errorf("nil rp: different-rack score (%v) should exceed same-rack score (%v)", diffRack, sameRack)
	}
}

func TestPlanBalanceDestination_ChoosesBestValidCompositeDestination(t *testing.T) {
	servers := []serverSpec{
		{id: "node-a", diskType: "hdd", diskID: 1, dc: "dc1", rack: "rack1"},
		{id: "node-b", diskType: "hdd", diskID: 2, dc: "dc1", rack: "rack3"},
		{id: "node-c", diskType: "hdd", diskID: 3, dc: "dc1", rack: "rack1"},
	}
	volumes := makeVolumesWith("node-a", "hdd", "dc1", "rack1", "c1", 1, 1, withReplicas(11))
	replicas := []types.ReplicaLocation{
		loc("dc1", "rack1", "node-a"),
		loc("dc1", "rack1", "node-d"),
		loc("dc1", "rack2", "node-e"),
	}

	plan, err := planBalanceDestination(buildTopology(servers, volumes), volumes[0], rp(t, "011"), replicas, map[string]int{
		"node-b": 0,
		"node-c": 0,
	})
	if err != nil {
		t.Fatalf("planBalanceDestination failed: %v", err)
	}
	if plan.TargetNode != "node-c" {
		t.Fatalf("expected valid same-rack destination node-c, got %s", plan.TargetNode)
	}
	if plan.TargetRack != "rack1" {
		t.Fatalf("expected rack1 destination, got %s", plan.TargetRack)
	}
}

func TestCreateBalanceTask_FallbackSelectsValidCompositeDestination(t *testing.T) {
	servers := []serverSpec{
		{id: "node-a", diskType: "hdd", diskID: 1, dc: "dc1", rack: "rack1"},
		{id: "node-b", diskType: "hdd", diskID: 2, dc: "dc1", rack: "rack3"},
		{id: "node-c", diskType: "hdd", diskID: 3, dc: "dc1", rack: "rack1"},
	}
	volumes := makeVolumesWith("node-a", "hdd", "dc1", "rack1", "c1", 1, 1, withReplicas(11))
	clusterInfo := &types.ClusterInfo{
		ActiveTopology: buildTopology(servers, volumes),
		VolumeReplicaMap: map[uint32][]types.ReplicaLocation{
			1: {
				loc("dc1", "rack1", "node-a"),
				loc("dc1", "rack1", "node-d"),
				loc("dc1", "rack2", "node-e"),
			},
		},
	}

	task, destination := createBalanceTask("hdd", volumes[0], clusterInfo, "node-b", map[string]int{
		"node-b": 0,
		"node-c": 0,
	})
	if task == nil {
		t.Fatal("expected a balance task")
	}
	if destination != "node-c" {
		t.Fatalf("expected fallback destination node-c, got %s", destination)
	}
	if len(task.TypedParams.Targets) != 1 {
		t.Fatalf("expected 1 target, got %d", len(task.TypedParams.Targets))
	}
	if got := task.TypedParams.Targets[0].Node; got != "node-c:8080" {
		t.Fatalf("expected target node-c:8080, got %s", got)
	}
}